Jump to content


Photo

Voltage issues with my Sirius

  • Please log in to reply
16 replies to this topic

#1 gustavo_sanchez

gustavo_sanchez

    Messenger

  • *****
  • Posts: 458
  • Joined: 30 Dec 2010
  • Loc: Puerto Rico, US

Posted 08 June 2013 - 10:19 PM

I am taking pictures right now at my dark site. My Sirius is showing a voltage Reading of 11.5V, but my voltmeter reading at the battery shows 12.64V. What could be happening? I am using a 101Ah deep cycle marine battery powering only the mount.

#2 gustavo_sanchez

gustavo_sanchez

    Messenger

  • *****
  • Posts: 458
  • Joined: 30 Dec 2010
  • Loc: Puerto Rico, US

Posted 09 June 2013 - 12:39 AM

I should add that the mount power light blinks slowly, as expected when there is low power being applied. However, that is not the case.

#3 frito

frito

    Apollo

  • -----
  • Posts: 1183
  • Joined: 05 Oct 2012
  • Loc: Fremont, CA

Posted 09 June 2013 - 09:20 AM

perhaps your batteries volt meter is inaccurate? or vise versa.

the LED on the Sirius will blink when slewing if you are really unbalanced as well. just throwing that out there but 11.5V is far from a dead car battery. once you start getting well under 11 then you can call it dead :)

#4 rmollise

rmollise

    Hubble

  • *****
  • Posts: 15396
  • Joined: 06 Jul 2007

Posted 09 June 2013 - 10:17 AM

I am taking pictures right now at my dark site. My Sirius is showing a voltage Reading of 11.5V, but my voltmeter reading at the battery shows 12.64V. What could be happening? I am using a 101Ah deep cycle marine battery powering only the mount.


The voltmeter feature in the SynScan controller has a bug. It is inaccurate. Don't worry about it.

#5 gustavo_sanchez

gustavo_sanchez

    Messenger

  • *****
  • Posts: 458
  • Joined: 30 Dec 2010
  • Loc: Puerto Rico, US

Posted 09 June 2013 - 11:19 AM

Thanks Uncle Rod for the information. Should I ignore the blinking light too? It blinks even when the mount is parked doing nothing.

#6 rmollise

rmollise

    Hubble

  • *****
  • Posts: 15396
  • Joined: 06 Jul 2007

Posted 09 June 2013 - 12:12 PM

Thanks Uncle Rod for the information. Should I ignore the blinking light too? It blinks even when the mount is parked doing nothing.


If you've got a blinking light, that does indeed indicate low voltage. The figure you gave for voltage at the battery indicates something's bad with the battery, especially if you are measuring it when it's not under load. Check connections and try a different battery. Even deep cell batteries go bad.

#7 gustavo_sanchez

gustavo_sanchez

    Messenger

  • *****
  • Posts: 458
  • Joined: 30 Dec 2010
  • Loc: Puerto Rico, US

Posted 09 June 2013 - 03:00 PM

I went to Batteries Plus and tested the battery. It is fine. It seems like the mount has something wrong, but I don't have any idea.

#8 rmollise

rmollise

    Hubble

  • *****
  • Posts: 15396
  • Joined: 06 Jul 2007

Posted 09 June 2013 - 04:30 PM

If anything is happening, it is likely a cable/connector issue.

#9 Phil Sherman

Phil Sherman

    Surveyor 1

  • -----
  • Posts: 1505
  • Joined: 07 Dec 2010
  • Loc: Cleveland, Ohio

Posted 10 June 2013 - 07:21 AM

I've run into the same issue with my Atlas mount and solved it by inserting a switching buck/boost voltage regulator between the battery and the mount. The regulator is set to produce 13.6V, what you get from a fully charged wet cell battery (surface charge) after it's just been charged. My mount is very happy to run on this voltage, which doesn't vary no matter what the battery is putting out.

The unit I used was found, I think, on ebaY and cost $10. It's a complete tiny circuit board that requires power in and out connections. For the electronics challenged, I also saw similar units that are mounted in a nice case, but at a higher price point. I also use similar sized buck switching regulators to generate 8 and 5 volts for a Canon camera and USB devices. I also added additional filter capacitors to the outputs of all of the regulators to help cut down electrical noise, a characteristic of these devices.

Phil

#10 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 43412
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 10 June 2013 - 07:40 AM

If you've got a blinking light, that does indeed indicate low voltage. The figure you gave for voltage at the battery indicates something's bad with the battery, especially if you are measuring it when it's not under load. Check connections and try a different battery. Even deep cell batteries go bad.



The voltmeter says the battery is 12.64 volts. That's pretty normal for a lead-acid battery. According to what I see, that indicates about 95% charge..

The Sirius says 11.5 volts and the light is flashing. If the Sirius is correct, that suggests a voltage drop of about 1.1 volts. At 1 amp current draw, that implies a resistance of about 1 ohm.. that's not much and could easily be the result of a poor connection...

If you can, measure the voltage at the mount versus at the battery. A volt meter is very handy for locating bad connections. Measure the voltages drops across various connections can cables.

Jon

#11 rmollise

rmollise

    Hubble

  • *****
  • Posts: 15396
  • Joined: 06 Jul 2007

Posted 10 June 2013 - 08:35 AM

I don't think it is correct Jon, as I said in my initial post, there is a known problem with the SynScan voltage readout.

#12 gustavo_sanchez

gustavo_sanchez

    Messenger

  • *****
  • Posts: 458
  • Joined: 30 Dec 2010
  • Loc: Puerto Rico, US

Posted 10 June 2013 - 07:36 PM

I checked the 12V DC power cable with an AC to DC power adapter to see if I saw any voltage irregularities, but the mount worked fine. It seems it's not the cable or interface related to it.

Next steps: update the controller firmware (seems like the voltage bug was fixed in one of the latest updates) and check out one of those voltage conditioner circuits.

#13 tclehman1969

tclehman1969

    Ranger 4

  • *****
  • Posts: 346
  • Joined: 18 May 2010
  • Loc: SF Bay Area, California

Posted 11 June 2013 - 01:36 AM

Fascinating. I took to the mountains a 101 amp/hr battery with me for my Atlas EQ-G mount. I ran for 2 hours or so the first night then on the second night ran about 2 more hours and started getting the blinking light and low voltage indicated on the hand controller. The battery had been fully charged prior to the first night out. In fact on night one, the hand controller indicated a battery voltage of about 12.4 volts. On the second night, I got the flashing led and checked the hand controller indicating 11.5 volts.

I didn't think to check the connection on the mount, wiggle it or something, as I had heard this can be a problem point. I am fairly certain I did the math correctly in that the Atlas EQ-G draws less than 2 amps/hr. my battery is a 101 amp/hr deep cycle which, I understand, should be able to withstand. 50 percent drain before needing recharging, so about 25 hrs in my case. Is this accurate?

#14 rmollise

rmollise

    Hubble

  • *****
  • Posts: 15396
  • Joined: 06 Jul 2007

Posted 11 June 2013 - 07:04 AM

Yes, with the proviso that it only draws that much current when it is slewing at full speed...

#15 gustavo_sanchez

gustavo_sanchez

    Messenger

  • *****
  • Posts: 458
  • Joined: 30 Dec 2010
  • Loc: Puerto Rico, US

Posted 11 June 2013 - 08:08 AM

Yes, with the proviso that it only draws that much current when it is slewing at full speed...


...which makes the situation much more perplexing! Almost the same in my case.

#16 Phil Sherman

Phil Sherman

    Surveyor 1

  • -----
  • Posts: 1505
  • Joined: 07 Dec 2010
  • Loc: Cleveland, Ohio

Posted 11 June 2013 - 07:41 PM

Fascinating. I took to the mountains a 101 amp/hr battery with me for my Atlas EQ-G mount. I ran for 2 hours or so the first night then on the second night ran about 2 more hours and started getting the blinking light and low voltage indicated on the hand controller. The battery had been fully charged prior to the first night out. In fact on night one, the hand controller indicated a battery voltage of about 12.4 volts. On the second night, I got the flashing led and checked the hand controller indicating 11.5 volts.

I didn't think to check the connection on the mount, wiggle it or something, as I had heard this can be a problem point. I am fairly certain I did the math correctly in that the Atlas EQ-G draws less than 2 amps/hr. my battery is a 101 amp/hr deep cycle which, I understand, should be able to withstand. 50 percent drain before needing recharging, so about 25 hrs in my case. Is this accurate?


Your 101AH battery probably has a bit less capacity than that. Manufacturers rate their batteries in different ways and most of the ones I've seen will be rated at a 1AH load. If you're drawing an average of 2AH, the life will be shorter. The only common rating you should believe (not trust) is the "reserve capacity" in minutes. The test for this is done at a 25A load and it specifies the starting and terminating conditions for the test. This makes it harder to fudge the results.

There's also no guarantee that your battery is in good shape. It's initial design capacity may have been 101AH but it's current capacity could be only 30-40AH, or less. The only wasy to test this is to charge the battery, let it sit for an hour, then put a reasonable load on it, ie. 10A, and measure the battery voltage every 5-10 minutes. End the test when the voltage, under load is 10.8V then calculate how much power you've drawn from the battery.

Wet cell batteries can be dmaaged in many ways. If the plates become uncovered, a low fluid condition, the battery capacity and life decrease rapidly. Leaving a battery partially charge for an extended period can also damage capacity. Storage at high temperatures isn't good for them either.

New batteries that come "dry" can also be damaged if they sit too long between manufacture and the initial add of fluid.

Phil

#17 tclehman1969

tclehman1969

    Ranger 4

  • *****
  • Posts: 346
  • Joined: 18 May 2010
  • Loc: SF Bay Area, California

Posted 11 June 2013 - 10:41 PM

Some batteries do list reserve capacity in the manner you describe, others don't. In this particular instance, the battery is listed as 101 amp hour capacity and no reserve capacity is provided.

But, on another note, I charged up the battery completely and then connected it to my Atlas. I checked the connections to make certain they were good. I started running the scope at 10:00 AM this morning and the voltage indicator on the hand controller showed 12.5 volts. During the day I let it run and ran it through some slews and also just drove the motors in RA and Dec as well. 10 hours later the Atlas was still running and the hand controller voltage indicated 12.4 volts. When I hit the slewing buttons it would drop to 12.2 volts and pop back up to 12.4 when I released it. I'd say nothing really wrong here. Most likely was a bad connection the other night when I got the low voltage reading. Ten hours of run time is more than enough for a typical observing night for me.






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics